<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    body>div{
      width: 200px;
      border: 1px solid red;
      overflow: hidden;
      /*当元素的所有子元素全部浮动时，自动识别的高度为0
     后面的元素会顶上来导致显示异常，添加overflow:hidden解决异常
     */
    }
    #d1{
      width: 50px;
      height: 50px;
      background-color: red;

      float: left;

    }
    #d2{
      width: 50px;
      height: 50px;
      background-color: green;
      float: left;
    }
    #d3{
      width: 50px;
      height: 50px;
      background-color: blue;
      float: right;
    }
  </style>
</head>
<body>
<div>
  <div id="d1"></div>
  <div id="d2"></div>
  <div id="d3"></div>
</div>
</body>
</html>